The emissions of NO, N2O, HCl, SO2 and CO were investigated during the combustion of coal and municipal refuse mixtures in a circulating fluidized bed boiler. The results show that the addition of municipal solid waste (MSW) leads to lower N2O and SO2 emissions. On the other hand, hydrogen chloride and nitric oxide concentrations increased with the amount of waste added. The variation of NO emissions with the mixture composition has been simply described by a model considering that NO is especially reduced by CO on the char surface. CO emissions slightly decrease when the MSW proportion is low, but when the chlorine supply is significant, inhibition of CO oxidation by HCl provokes the opposite trend: a growth in CO concentration.